@ -182,15 +182,44 @@ struct key_compare_to_adapter<std::greater<absl::Cord>> {
using type = StringBtreeDefaultGreater ; using type = StringBtreeDefaultGreater ;
} ; } ;
// Detects an 'absl_btree_prefer_linear_node_search' member. This is
// a protocol used as an opt-in or opt-out of linear search.
//
// For example, this would be useful for key types that wrap an integer
// and define their own cheap operator<(). For example:
//
// class K {
// public:
// using absl_btree_prefer_linear_node_search = std::true_type;
// ...
// private:
// friend bool operator<(K a, K b) { return a.k_ < b.k_; }
// int k_;
// };
//
// btree_map<K, V> m; // Uses linear search
//
// If T has the preference tag, then it has a preference.
// Btree will use the tag's truth value.
template < typename T , typename = void >
struct has_linear_node_search_preference : std : : false_type { } ;
template < typename T , typename = void >
struct prefers_linear_node_search : std : : false_type { } ;
template < typename T >
struct has_linear_node_search_preference <
T , absl : : void_t < typename T : : absl_btree_prefer_linear_node_search > >
: std : : true_type { } ;
template < typename T >
struct prefers_linear_node_search <
T , absl : : void_t < typename T : : absl_btree_prefer_linear_node_search > >
: T : : absl_btree_prefer_linear_node_search { } ;
template < typename Key , typename Compare , typename Alloc , int TargetNodeSize , template < typename Key , typename Compare , typename Alloc , int TargetNodeSize ,
bool Multi , typename SlotPolicy > bool Multi , typename SlotPolicy >
struct common_params { struct common_params {
// If Compare is a common comparator for a string-like type, then we adapt it
// If Compare is a common comparator for a string-like type, then we adapt it
// to use heterogeneous lookup and to be a key-compare-to comparator.
// to use heterogeneous lookup and to be a key-compare-to comparator.
using key_compare = typename key_compare_to_adapter < Compare > : : type ; using key_compare = typename key_compare_to_adapter < Compare > : : type ;
// True when key_compare has been adapted to StringBtreeDefault{Less,Greater}.
using is_key_compare_adapted =
absl : : negation < std : : is_same < key_compare , Compare > > ;
// A type which indicates if we have a key-compare-to functor or a plain old
// A type which indicates if we have a key-compare-to functor or a plain old
// key-compare functor.
// key-compare functor.
using is_key_compare_to = btree_is_key_compare_to < key_compare , Key > ; using is_key_compare_to = btree_is_key_compare_to < key_compare , Key > ;
@ -200,9 +229,6 @@ struct common_params {
using size_type = std : : make_signed < size_t > : : type ; using size_type = std : : make_signed < size_t > : : type ;
using difference_type = ptrdiff_t ; using difference_type = ptrdiff_t ;
// True if this is a multiset or multimap.
using is_multi_container = std : : integral_constant < bool , Multi > ;
using slot_policy = SlotPolicy ; using slot_policy = SlotPolicy ;
using slot_type = typename slot_policy : : slot_type ; using slot_type = typename slot_policy : : slot_type ;
using value_type = typename slot_policy : : value_type ; using value_type = typename slot_policy : : value_type ;
@ -212,6 +238,23 @@ struct common_params {
using reference = value_type & ; using reference = value_type & ;
using const_reference = const value_type & ; using const_reference = const value_type & ;
// For the given lookup key type, returns whether we can have multiple
// equivalent keys in the btree. If this is a multi-container, then we can.
// Otherwise, we can have multiple equivalent keys only if all of the
// following conditions are met:
// - The comparator is transparent.
// - The lookup key type is not the same as key_type.
// - The comparator is not a StringBtreeDefault{Less,Greater} comparator
// that we know has the same equivalence classes for all lookup types.
template < typename LookupKey >
constexpr static bool can_have_multiple_equivalent_keys ( ) {
return Multi | |
( IsTransparent < key_compare > : : value & &
! std : : is_same < LookupKey , Key > : : value & &
! std : : is_same < key_compare , StringBtreeDefaultLess > : : value & &
! std : : is_same < key_compare , StringBtreeDefaultGreater > : : value ) ;
}
enum { enum {
kTargetNodeSize = TargetNodeSize , kTargetNodeSize = TargetNodeSize ,
@ -391,6 +434,10 @@ struct SearchResult {
// useful information.
// useful information.
template < typename V > template < typename V >
struct SearchResult < V , false > { struct SearchResult < V , false > {
SearchResult ( ) { }
explicit SearchResult ( V value ) : value ( value ) { }
SearchResult ( V value , MatchKind /*match*/ ) : value ( value ) { }
V value ; V value ;
static constexpr bool HasMatch ( ) { return false ; } static constexpr bool HasMatch ( ) { return false ; }
@ -403,7 +450,6 @@ struct SearchResult<V, false> {
template < typename Params > template < typename Params >
class btree_node { class btree_node {
using is_key_compare_to = typename Params : : is_key_compare_to ; using is_key_compare_to = typename Params : : is_key_compare_to ;
using is_multi_container = typename Params : : is_multi_container ;
using field_type = typename Params : : node_count_type ; using field_type = typename Params : : node_count_type ;
using allocator_type = typename Params : : allocator_type ; using allocator_type = typename Params : : allocator_type ;
using slot_type = typename Params : : slot_type ; using slot_type = typename Params : : slot_type ;
@ -421,15 +467,22 @@ class btree_node {
using difference_type = typename Params : : difference_type ; using difference_type = typename Params : : difference_type ;
// Btree decides whether to use linear node search as follows:
// Btree decides whether to use linear node search as follows:
// - If the comparator expresses a preference, use that.
// - If the key expresses a preference, use that.
// - If the key is arithmetic and the comparator is std::less or
// - If the key is arithmetic and the comparator is std::less or
// std::greater, choose linear.
// std::greater, choose linear.
// - Otherwise, choose binary.
// - Otherwise, choose binary.
// TODO(ezb): Might make sense to add condition(s) based on node-size.
// TODO(ezb): Might make sense to add condition(s) based on node-size.
using use_linear_search = std : : integral_constant < using use_linear_search = std : : integral_constant <
bool , bool ,
std : : is_arithmetic < key_type > : : value & & has_linear_node_search_preference < key_compare > : : value
( std : : is_same < std : : less < key_type > , key_compare > : : value | | ? prefers_linear_node_search < key_compare > : : value
std : : is_same < std : : greater < key_type > , key_compare > : : value ) > ; : has_linear_node_search_preference < key_type > : : value
? prefers_linear_node_search < key_type > : : value
: std : : is_arithmetic < key_type > : : value & &
( std : : is_same < std : : less < key_type > , key_compare > : : value | |
std : : is_same < std : : greater < key_type > ,
key_compare > : : value ) > ;
// This class is organized by gtl::Layout as if it had the following
// This class is organized by gtl::Layout as if it had the following
// structure:
// structure:
@ -446,23 +499,23 @@ class btree_node {
// // is the same as the count of values.
// // is the same as the count of values.
// field_type finish;
// field_type finish;
// // The maximum number of values the node can hold. This is an integer in
// // The maximum number of values the node can hold. This is an integer in
// // [1, kNodeValues] for root leaf nodes, kNodeValue s for non-root leaf
// // [1, kNodeSlots] for root leaf nodes, kNodeSlot s for non-root leaf
// // nodes, and kInternalNodeMaxCount (as a sentinel value) for internal
// // nodes, and kInternalNodeMaxCount (as a sentinel value) for internal
// // nodes (even though there are still kNodeValue s values in the node).
// // nodes (even though there are still kNodeSlot s values in the node).
// // TODO(ezb): make max_count use only 4 bits and record log2(capacity)
// // TODO(ezb): make max_count use only 4 bits and record log2(capacity)
// // to free extra bits for is_root, etc.
// // to free extra bits for is_root, etc.
// field_type max_count;
// field_type max_count;
//
//
// // The array of values. The capacity is `max_count` for leaf nodes and
// // The array of values. The capacity is `max_count` for leaf nodes and
// // kNodeValue s for internal nodes. Only the values in
// // kNodeSlot s for internal nodes. Only the values in
// // [start, finish) have been initialized and are valid.
// // [start, finish) have been initialized and are valid.
// slot_type values[max_count];
// slot_type values[max_count];
//
//
// // The array of child pointers. The keys in children[i] are all less
// // The array of child pointers. The keys in children[i] are all less
// // than key(i). The keys in children[i + 1] are all greater than key(i).
// // than key(i). The keys in children[i + 1] are all greater than key(i).
// // There are 0 children for leaf nodes and kNodeValue s + 1 children for
// // There are 0 children for leaf nodes and kNodeSlot s + 1 children for
// // internal nodes.
// // internal nodes.
// btree_node *children[kNodeValue s + 1];
// btree_node *children[kNodeSlot s + 1];
//
//
// This class is only constructed by EmptyNodeType. Normally, pointers to the
// This class is only constructed by EmptyNodeType. Normally, pointers to the
// layout above are allocated, cast to btree_node*, and de-allocated within
// layout above are allocated, cast to btree_node*, and de-allocated within
@ -484,57 +537,62 @@ class btree_node {
private : private :
using layout_type = absl : : container_internal : : Layout < btree_node * , field_type , using layout_type = absl : : container_internal : : Layout < btree_node * , field_type ,
slot_type , btree_node * > ; slot_type , btree_node * > ;
constexpr static size_type SizeWithNValue s ( size_type n ) { constexpr static size_type SizeWithNSlot s ( size_type n ) {
return layout_type ( /*parent*/ 1 , return layout_type ( /*parent*/ 1 ,
/*position, start, finish, max_count*/ 4 , /*position, start, finish, max_count*/ 4 ,
/*value s*/ n , /*slot s*/ n ,
/*children*/ 0 ) /*children*/ 0 )
. AllocSize ( ) ; . AllocSize ( ) ;
} }
// A lower bound for the overhead of fields other than values in a leaf node.
// A lower bound for the overhead of fields other than values in a leaf node.
constexpr static size_type MinimumOverhead ( ) { constexpr static size_type MinimumOverhead ( ) {
return SizeWithNValue s ( 1 ) - sizeof ( value_type ) ; return SizeWithNSlot s ( 1 ) - sizeof ( value_type ) ;
} }
// Compute how many values we can fit onto a leaf node taking into account
// Compute how many values we can fit onto a leaf node taking into account
// padding.
// padding.
constexpr static size_type NodeTargetValue s ( const int begin , const int end ) { constexpr static size_type NodeTargetSlot s ( const int begin , const int end ) {
return begin = = end ? begin return begin = = end ? begin
: SizeWithNValue s ( ( begin + end ) / 2 + 1 ) > : SizeWithNSlot s ( ( begin + end ) / 2 + 1 ) >
params_type : : kTargetNodeSize params_type : : kTargetNodeSize
? NodeTargetValue s ( begin , ( begin + end ) / 2 ) ? NodeTargetSlot s ( begin , ( begin + end ) / 2 )
: NodeTargetValue s ( ( begin + end ) / 2 + 1 , end ) ; : NodeTargetSlot s ( ( begin + end ) / 2 + 1 , end ) ;
} }
enum { enum {
kTargetNodeSize = params_type : : kTargetNodeSize , kTargetNodeSize = params_type : : kTargetNodeSize ,
kNodeTargetValues = NodeTargetValue s ( 0 , params_type : : kTargetNodeSize ) , kNodeTargetSlots = NodeTargetSlot s ( 0 , params_type : : kTargetNodeSize ) ,
// We need a minimum of 3 value s per internal node in order to perform
// We need a minimum of 3 slot s per internal node in order to perform
// splitting (1 value for the two nodes involved in the split and 1 value
// splitting (1 value for the two nodes involved in the split and 1 value
// propagated to the parent as the delimiter for the split).
// propagated to the parent as the delimiter for the split). For performance
kNodeValues = kNodeTargetValues > = 3 ? kNodeTargetValues : 3 , // reasons, we don't allow 3 slots-per-node due to bad worst case occupancy
// of 1/3 (for a node, not a b-tree).
kMinNodeSlots = 4 ,
kNodeSlots =
kNodeTargetSlots > = kMinNodeSlots ? kNodeTargetSlots : kMinNodeSlots ,
// The node is internal (i.e. is not a leaf node) if and only if `max_count`
// The node is internal (i.e. is not a leaf node) if and only if `max_count`
// has this value.
// has this value.
kInternalNodeMaxCount = 0 , kInternalNodeMaxCount = 0 ,
} ; } ;
// Leaves can have less than kNodeValue s values.
// Leaves can have less than kNodeSlot s values.
constexpr static layout_type LeafLayout ( const int max_values = kNodeValue s) { constexpr static layout_type LeafLayout ( const int slot_count = kNodeSlot s) {
return layout_type ( /*parent*/ 1 , return layout_type ( /*parent*/ 1 ,
/*position, start, finish, max_count*/ 4 , /*position, start, finish, max_count*/ 4 ,
/*values*/ max_values , /*slots*/ slot_count ,
/*children*/ 0 ) ; /*children*/ 0 ) ;
} }
constexpr static layout_type InternalLayout ( ) { constexpr static layout_type InternalLayout ( ) {
return layout_type ( /*parent*/ 1 , return layout_type ( /*parent*/ 1 ,
/*position, start, finish, max_count*/ 4 , /*position, start, finish, max_count*/ 4 ,
/*values*/ kNodeValue s , /*slots*/ kNodeSlot s ,
/*children*/ kNodeValue s + 1 ) ; /*children*/ kNodeSlot s + 1 ) ;
} }
constexpr static size_type LeafSize ( const int max_values = kNodeValue s) { constexpr static size_type LeafSize ( const int slot_count = kNodeSlot s) {
return LeafLayout ( max_values ) . AllocSize ( ) ; return LeafLayout ( slot_count ) . AllocSize ( ) ;
} }
constexpr static size_type InternalSize ( ) { constexpr static size_type InternalSize ( ) {
return InternalLayout ( ) . AllocSize ( ) ; return InternalLayout ( ) . AllocSize ( ) ;
@ -591,10 +649,10 @@ class btree_node {
} }
field_type max_count ( ) const { field_type max_count ( ) const {
// Internal nodes have max_count==kInternalNodeMaxCount.
// Internal nodes have max_count==kInternalNodeMaxCount.
// Leaf nodes have max_count in [1, kNodeValue s].
// Leaf nodes have max_count in [1, kNodeSlot s].
const field_type max_count = GetField < 1 > ( ) [ 3 ] ; const field_type max_count = GetField < 1 > ( ) [ 3 ] ;
return max_count = = field_type { kInternalNodeMaxCount } return max_count = = field_type { kInternalNodeMaxCount }
? field_type { kNodeValue s } ? field_type { kNodeSlot s }
: max_count ; : max_count ;
} }
@ -672,7 +730,7 @@ class btree_node {
} }
+ + s ; + + s ;
} }
return { s } ; return SearchResult < int , false > { s } ;
} }
// Returns the position of the first value whose key is not less than k using
// Returns the position of the first value whose key is not less than k using
@ -707,7 +765,7 @@ class btree_node {
e = mid ; e = mid ;
} }
} }
return { s } ; return SearchResult < int , false > { s } ;
} }
// Returns the position of the first value whose key is not less than k using
// Returns the position of the first value whose key is not less than k using
@ -716,7 +774,7 @@ class btree_node {
SearchResult < int , true > binary_search_impl ( SearchResult < int , true > binary_search_impl (
const K & k , int s , int e , const CompareTo & comp , const K & k , int s , int e , const CompareTo & comp ,
std : : true_type /* IsCompareTo */ ) const { std : : true_type /* IsCompareTo */ ) const {
if ( is_multi_container : : value ) { if ( params_type : : template can_have_multiple_equivalent_keys < K > ( ) ) {
MatchKind exact_match = MatchKind : : kNe ; MatchKind exact_match = MatchKind : : kNe ;
while ( s ! = e ) { while ( s ! = e ) {
const int mid = ( s + e ) > > 1 ; const int mid = ( s + e ) > > 1 ;
@ -727,14 +785,14 @@ class btree_node {
e = mid ; e = mid ;
if ( c = = 0 ) { if ( c = = 0 ) {
// Need to return the first value whose key is not less than k,
// Need to return the first value whose key is not less than k,
// which requires continuing the binary search if this is a
// which requires continuing the binary search if there could be
// multi-container .
// multiple equivalent keys .
exact_match = MatchKind : : kEq ; exact_match = MatchKind : : kEq ;
} }
} }
} }
return { s , exact_match } ; return { s , exact_match } ;
} else { // Not a multi-container .
} else { // Can't have multiple equivalent keys .
while ( s ! = e ) { while ( s ! = e ) {
const int mid = ( s + e ) > > 1 ; const int mid = ( s + e ) > > 1 ;
const absl : : weak_ordering c = comp ( key ( mid ) , k ) ; const absl : : weak_ordering c = comp ( key ( mid ) , k ) ;
@ -784,12 +842,12 @@ class btree_node {
start_slot ( ) , max_count * sizeof ( slot_type ) ) ; start_slot ( ) , max_count * sizeof ( slot_type ) ) ;
} }
void init_internal ( btree_node * parent ) { void init_internal ( btree_node * parent ) {
init_leaf ( parent , kNodeValue s ) ; init_leaf ( parent , kNodeSlot s ) ;
// Set `max_count` to a sentinel value to indicate that this node is
// Set `max_count` to a sentinel value to indicate that this node is
// internal.
// internal.
set_max_count ( kInternalNodeMaxCount ) ; set_max_count ( kInternalNodeMaxCount ) ;
absl : : container_internal : : SanitizerPoisonMemoryRegion ( absl : : container_internal : : SanitizerPoisonMemoryRegion (
& mutable_child ( start ( ) ) , ( kNodeValue s + 1 ) * sizeof ( btree_node * ) ) ; & mutable_child ( start ( ) ) , ( kNodeSlot s + 1 ) * sizeof ( btree_node * ) ) ;
} }
static void deallocate ( const size_type size , btree_node * node , static void deallocate ( const size_type size , btree_node * node ,
@ -800,12 +858,6 @@ class btree_node {
// Deletes a node and all of its children.
// Deletes a node and all of its children.
static void clear_and_delete ( btree_node * node , allocator_type * alloc ) ; static void clear_and_delete ( btree_node * node , allocator_type * alloc ) ;
public :
// Exposed only for tests.
static bool testonly_uses_linear_node_search ( ) {
return use_linear_search : : value ;
}
private : private :
template < typename . . . Args > template < typename . . . Args >
void value_init ( const field_type i , allocator_type * alloc , Args & & . . . args ) { void value_init ( const field_type i , allocator_type * alloc , Args & & . . . args ) {
@ -873,6 +925,7 @@ struct btree_iterator {
using key_type = typename Node : : key_type ; using key_type = typename Node : : key_type ;
using size_type = typename Node : : size_type ; using size_type = typename Node : : size_type ;
using params_type = typename Node : : params_type ; using params_type = typename Node : : params_type ;
using is_map_container = typename params_type : : is_map_container ;
using node_type = Node ; using node_type = Node ;
using normal_node = typename std : : remove_const < Node > : : type ; using normal_node = typename std : : remove_const < Node > : : type ;
@ -884,7 +937,7 @@ struct btree_iterator {
using slot_type = typename params_type : : slot_type ; using slot_type = typename params_type : : slot_type ;
using iterator = using iterator =
btree_iterator < normal_node , normal_reference , normal_pointer > ; btree_iterator < normal_node , normal_reference , normal_pointer > ;
using const_iterator = using const_iterator =
btree_iterator < const_node , const_reference , const_pointer > ; btree_iterator < const_node , const_reference , const_pointer > ;
@ -901,20 +954,19 @@ struct btree_iterator {
btree_iterator ( Node * n , int p ) : node ( n ) , position ( p ) { } btree_iterator ( Node * n , int p ) : node ( n ) , position ( p ) { }
// NOTE: this SFINAE allows for implicit conversions from iterator to
// NOTE: this SFINAE allows for implicit conversions from iterator to
// const_iterator, but it specifically avoids defining copy constructors so
// const_iterator, but it specifically avoids hiding the copy constructor so
// that btree_iterator can be trivially copyable. This is for performance and
// that the trivial one will be used when possible.
// binary size reasons.
template < typename N , typename R , typename P , template < typename N , typename R , typename P ,
absl : : enable_if_t < absl : : enable_if_t <
std : : is_same < btree_iterator < N , R , P > , iterator > : : value & & std : : is_same < btree_iterator < N , R , P > , iterator > : : value & &
std : : is_same < btree_iterator , const_iterator > : : value , std : : is_same < btree_iterator , const_iterator > : : value ,
int > = 0 > int > = 0 >
btree_iterator ( const btree_iterator < N , R , P > & other ) // NOLINT
btree_iterator ( const btree_iterator < N , R , P > other ) // NOLINT
: node ( other . node ) , position ( other . position ) { } : node ( other . node ) , position ( other . position ) { }
private : private :
// This SFINAE allows explicit conversions from const_iterator to
// This SFINAE allows explicit conversions from const_iterator to
// iterator, but also avoids defining a copy constructor.
// iterator, but also avoids hiding the copy constructor.
// NOTE: the const_cast is safe because this constructor is only called by
// NOTE: the const_cast is safe because this constructor is only called by
// non-const methods and the container owns the nodes.
// non-const methods and the container owns the nodes.
template < typename N , typename R , typename P , template < typename N , typename R , typename P ,
@ -922,7 +974,7 @@ struct btree_iterator {
std : : is_same < btree_iterator < N , R , P > , const_iterator > : : value & & std : : is_same < btree_iterator < N , R , P > , const_iterator > : : value & &
std : : is_same < btree_iterator , iterator > : : value , std : : is_same < btree_iterator , iterator > : : value ,
int > = 0 > int > = 0 >
explicit btree_iterator ( const btree_iterator < N , R , P > & other ) explicit btree_iterator ( const btree_iterator < N , R , P > other )
: node ( const_cast < node_type * > ( other . node ) ) , position ( other . position ) { } : node ( const_cast < node_type * > ( other . node ) ) , position ( other . position ) { }
// Increment/decrement the iterator.
// Increment/decrement the iterator.
@ -985,6 +1037,8 @@ struct btree_iterator {
} }
private : private :
friend iterator ;
friend const_iterator ;
template < typename Params > template < typename Params >
friend class btree ; friend class btree ;
template < typename Tree > template < typename Tree >
@ -995,8 +1049,6 @@ struct btree_iterator {
friend class btree_map_container ; friend class btree_map_container ;
template < typename Tree > template < typename Tree >
friend class btree_multiset_container ; friend class btree_multiset_container ;
template < typename N , typename R , typename P >
friend struct btree_iterator ;
template < typename TreeType , typename CheckerType > template < typename TreeType , typename CheckerType >
friend class base_checker ; friend class base_checker ;
@ -1017,8 +1069,6 @@ class btree {
using is_key_compare_to = typename Params : : is_key_compare_to ; using is_key_compare_to = typename Params : : is_key_compare_to ;
using init_type = typename Params : : init_type ; using init_type = typename Params : : init_type ;
using field_type = typename node_type : : field_type ; using field_type = typename node_type : : field_type ;
using is_multi_container = typename Params : : is_multi_container ;
using is_key_compare_adapted = typename Params : : is_key_compare_adapted ;
// We use a static empty node for the root/leftmost/rightmost of empty btrees
// We use a static empty node for the root/leftmost/rightmost of empty btrees
// in order to avoid branching in begin()/end().
// in order to avoid branching in begin()/end().
@ -1054,8 +1104,8 @@ class btree {
} }
enum : uint32_t { enum : uint32_t {
kNodeValue s = node_type : : kNodeValue s , kNodeSlot s = node_type : : kNodeSlot s ,
kMinNodeValues = kNodeValue s / 2 , kMinNodeValues = kNodeSlot s / 2 ,
} ; } ;
struct node_stats { struct node_stats {
@ -1085,7 +1135,8 @@ class btree {
using const_reference = typename Params : : const_reference ; using const_reference = typename Params : : const_reference ;
using pointer = typename Params : : pointer ; using pointer = typename Params : : pointer ;
using const_pointer = typename Params : : const_pointer ; using const_pointer = typename Params : : const_pointer ;
using iterator = btree_iterator < node_type , reference , pointer > ; using iterator =
typename btree_iterator < node_type , reference , pointer > : : iterator ;
using const_iterator = typename iterator : : const_iterator ; using const_iterator = typename iterator : : const_iterator ;
using reverse_iterator = std : : reverse_iterator < iterator > ; using reverse_iterator = std : : reverse_iterator < iterator > ;
using const_reverse_iterator = std : : reverse_iterator < const_iterator > ; using const_reverse_iterator = std : : reverse_iterator < const_iterator > ;
@ -1098,28 +1149,46 @@ class btree {
private : private :
// For use in copy_or_move_values_in_order.
// For use in copy_or_move_values_in_order.
const value_type & maybe_move_from_iterator ( const_iterator it ) { return * it ; } const value_type & maybe_move_from_iterator ( const_iterator it ) { return * it ; }
value_type & & maybe_move_from_iterator ( iterator it ) { return std : : move ( * it ) ; } value_type & & maybe_move_from_iterator ( iterator it ) {
// This is a destructive operation on the other container so it's safe for
// us to const_cast and move from the keys here even if it's a set.
return std : : move ( const_cast < value_type & > ( * it ) ) ;
}
// Copies or moves (depending on the template parameter) the values in
// Copies or moves (depending on the template parameter) the values in
// other into this btree in their order in other. This btree must be empty
// other into this btree in their order in other. This btree must be empty
// before this method is called. This method is used in copy construction,
// before this method is called. This method is used in copy construction,
// copy assignment, and move assignment.
// copy assignment, and move assignment.
template < typename Btree > template < typename Btree >
void copy_or_move_values_in_order ( Btree * other ) ; void copy_or_move_values_in_order ( Btree & other ) ;
// Validates that various assumptions/requirements are true at compile time.
// Validates that various assumptions/requirements are true at compile time.
constexpr static bool static_assert_validation ( ) ; constexpr static bool static_assert_validation ( ) ;
public : public :
btree ( const key_compare & comp , const allocator_type & alloc ) ; btree ( const key_compare & comp , const allocator_type & alloc )
: root_ ( comp , alloc , EmptyNode ( ) ) , rightmost_ ( EmptyNode ( ) ) , size_ ( 0 ) { }
btree ( const btree & other ) ; btree ( const btree & other ) : btree ( other , other . allocator ( ) ) { }
btree ( const btree & other , const allocator_type & alloc )
: btree ( other . key_comp ( ) , alloc ) {
copy_or_move_values_in_order ( other ) ;
}
btree ( btree & & other ) noexcept btree ( btree & & other ) noexcept
: root_ ( std : : move ( other . root_ ) ) , : root_ ( std : : move ( other . root_ ) ) ,
rightmost_ ( absl : : exchange ( other . rightmost_ , EmptyNode ( ) ) ) , rightmost_ ( absl : : exchange ( other . rightmost_ , EmptyNode ( ) ) ) ,
size_ ( absl : : exchange ( other . size_ , 0 ) ) { size_ ( absl : : exchange ( other . size_ , 0 ) ) {
other . mutable_root ( ) = EmptyNode ( ) ; other . mutable_root ( ) = EmptyNode ( ) ;
} }
btree ( btree & & other , const allocator_type & alloc )
: btree ( other . key_comp ( ) , alloc ) {
if ( alloc = = other . allocator ( ) ) {
swap ( other ) ;
} else {
// Move values from `other` one at a time when allocators are different.
copy_or_move_values_in_order ( other ) ;
}
}
~ btree ( ) { ~ btree ( ) {
// Put static_asserts in destructor to avoid triggering them before the type
// Put static_asserts in destructor to avoid triggering them before the type
@ -1147,17 +1216,22 @@ class btree {
return const_reverse_iterator ( begin ( ) ) ; return const_reverse_iterator ( begin ( ) ) ;
} }
// Finds the first element whose key is not less than key.
// Finds the first element whose key is not less than ` key` .
template < typename K > template < typename K >
iterator lower_bound ( const K & key ) { iterator lower_bound ( const K & key ) {
return internal_end ( internal_lower_bound ( key ) ) ; return internal_end ( internal_lower_bound ( key ) . value ) ;
} }
template < typename K > template < typename K >
const_iterator lower_bound ( const K & key ) const { const_iterator lower_bound ( const K & key ) const {
return internal_end ( internal_lower_bound ( key ) ) ; return internal_end ( internal_lower_bound ( key ) . value ) ;
} }
// Finds the first element whose key is greater than key.
// Finds the first element whose key is not less than `key` and also returns
// whether that element is equal to `key`.
template < typename K >
std : : pair < iterator , bool > lower_bound_equal ( const K & key ) const ;
// Finds the first element whose key is greater than `key`.
template < typename K > template < typename K >
iterator upper_bound ( const K & key ) { iterator upper_bound ( const K & key ) {
return internal_end ( internal_upper_bound ( key ) ) ; return internal_end ( internal_upper_bound ( key ) ) ;
@ -1239,18 +1313,8 @@ class btree {
// to the element after the last erased element.
// to the element after the last erased element.
std : : pair < size_type , iterator > erase_range ( iterator begin , iterator end ) ; std : : pair < size_type , iterator > erase_range ( iterator begin , iterator end ) ;
// Erases the specified key from the btree. Returns 1 if an element was
// Finds an element with key equivalent to `key` or returns `end()` if `key`
// erased and 0 otherwise.
// is not present.
template < typename K >
size_type erase_unique ( const K & key ) ;
// Erases all of the entries matching the specified key from the
// btree. Returns the number of elements erased.
template < typename K >
size_type erase_multi ( const K & key ) ;
// Finds the iterator corresponding to a key or returns end() if the key is
// not present.
template < typename K > template < typename K >
iterator find ( const K & key ) { iterator find ( const K & key ) {
return internal_end ( internal_find ( key ) ) ; return internal_end ( internal_find ( key ) ) ;
@ -1260,23 +1324,6 @@ class btree {
return internal_end ( internal_find ( key ) ) ; return internal_end ( internal_find ( key ) ) ;
} }
// Returns a count of the number of times the key appears in the btree.
template < typename K >
size_type count_unique ( const K & key ) const {
const iterator begin = internal_find ( key ) ;
if ( begin . node = = nullptr ) {
// The key doesn't exist in the tree.
return 0 ;
}
return 1 ;
}
// Returns a count of the number of times the key appears in the btree.
template < typename K >
size_type count_multi ( const K & key ) const {
const auto range = equal_range ( key ) ;
return std : : distance ( range . first , range . second ) ;
}
// Clear the btree, deleting all of the values it contains.
// Clear the btree, deleting all of the values it contains.
void clear ( ) ; void clear ( ) ;
@ -1339,12 +1386,14 @@ class btree {
} }
} }
// The average number of bytes used per value stored in the btree.
// The average number of bytes used per value stored in the btree assuming
// random insertion order.
static double average_bytes_per_value ( ) { static double average_bytes_per_value ( ) {
// Returns the number of bytes per value on a leaf node that is 75%
// The expected number of values per node with random insertion order is the
// full. Experimentally, this matches up nicely with the computed number of
// average of the maximum and minimum numbers of values per node.
// bytes per value in trees that had their values inserted in random order.
const double expected_values_per_node =
return node_type : : LeafSize ( ) / ( kNodeValues * 0.75 ) ; ( kNodeSlots + kMinNodeValues ) / 2.0 ;
return node_type : : LeafSize ( ) / expected_values_per_node ;
} }
// The fullness of the btree. Computed as the number of elements in the btree
// The fullness of the btree. Computed as the number of elements in the btree
@ -1354,7 +1403,7 @@ class btree {
// Returns 0 for empty trees.
// Returns 0 for empty trees.
double fullness ( ) const { double fullness ( ) const {
if ( empty ( ) ) return 0.0 ; if ( empty ( ) ) return 0.0 ;
return static_cast < double > ( size ( ) ) / ( nodes ( ) * kNodeValue s ) ; return static_cast < double > ( size ( ) ) / ( nodes ( ) * kNodeSlot s ) ;
} }
// The overhead of the btree structure in bytes per node. Computed as the
// The overhead of the btree structure in bytes per node. Computed as the
// total number of bytes used by the btree minus the number of bytes used for
// total number of bytes used by the btree minus the number of bytes used for
@ -1404,7 +1453,7 @@ class btree {
} }
node_type * new_leaf_node ( node_type * parent ) { node_type * new_leaf_node ( node_type * parent ) {
node_type * n = allocate ( node_type : : LeafSize ( ) ) ; node_type * n = allocate ( node_type : : LeafSize ( ) ) ;
n - > init_leaf ( parent , kNodeValue s ) ; n - > init_leaf ( parent , kNodeSlot s ) ;
return n ; return n ;
} }
node_type * new_leaf_root_node ( const int max_count ) { node_type * new_leaf_root_node ( const int max_count ) {
@ -1453,28 +1502,19 @@ class btree {
static IterType internal_last ( IterType iter ) ; static IterType internal_last ( IterType iter ) ;
// Returns an iterator pointing to the leaf position at which key would
// Returns an iterator pointing to the leaf position at which key would
// reside in the tree. We provide 2 versions of internal_locate. The first
// reside in the tree, unless there is an exact match - in which case, the
// version uses a less-than comparator and is incapable of distinguishing when
// result may not be on a leaf. When there's a three-way comparator, we can
// there is an exact match. The second version is for the key-compare-to
// return whether there was an exact match. This allows the caller to avoid a
// specialization and distinguishes exact matches. The key-compare-to
// subsequent comparison to determine if an exact match was made, which is
// specialization allows the caller to avoid a subsequent comparison to
// important for keys with expensive comparison, such as strings.
// determine if an exact match was made, which is important for keys with
// expensive comparison, such as strings.
template < typename K > template < typename K >
SearchResult < iterator , is_key_compare_to : : value > internal_locate ( SearchResult < iterator , is_key_compare_to : : value > internal_locate (
const K & key ) const ; const K & key ) const ;
template < typename K >
SearchResult < iterator , false > internal_locate_impl (
const K & key , std : : false_type /* IsCompareTo */ ) const ;
template < typename K >
SearchResult < iterator , true > internal_locate_impl (
const K & key , std : : true_type /* IsCompareTo */ ) const ;
// Internal routine which implements lower_bound().
// Internal routine which implements lower_bound().
template < typename K > template < typename K >
iterator internal_lower_bound ( const K & key ) const ; SearchResult < iterator , is_key_compare_to : : value > internal_lower_bound (
const K & key ) const ;
// Internal routine which implements upper_bound().
// Internal routine which implements upper_bound().
template < typename K > template < typename K >
@ -1503,13 +1543,6 @@ class btree {
return res ; return res ;
} }
public :
// Exposed only for tests.
static bool testonly_uses_linear_node_search ( ) {
return node_type : : testonly_uses_linear_node_search ( ) ;
}
private :
// We use compressed tuple in order to save space because key_compare and
// We use compressed tuple in order to save space because key_compare and
// allocator_type are usually empty.
// allocator_type are usually empty.
absl : : container_internal : : CompressedTuple < key_compare , allocator_type , absl : : container_internal : : CompressedTuple < key_compare , allocator_type ,
@ -1665,7 +1698,7 @@ template <typename P>
void btree_node < P > : : split ( const int insert_position , btree_node * dest , void btree_node < P > : : split ( const int insert_position , btree_node * dest ,
allocator_type * alloc ) { allocator_type * alloc ) {
assert ( dest - > count ( ) = = 0 ) ; assert ( dest - > count ( ) = = 0 ) ;
assert ( max_count ( ) = = kNodeValue s ) ; assert ( max_count ( ) = = kNodeSlot s ) ;
// We bias the split based on the position being inserted. If we're
// We bias the split based on the position being inserted. If we're
// inserting at the beginning of the left node then bias the split to put
// inserting at the beginning of the left node then bias the split to put
@ -1673,7 +1706,7 @@ void btree_node<P>::split(const int insert_position, btree_node *dest,
// right node then bias the split to put more values on the left node.
// right node then bias the split to put more values on the left node.
if ( insert_position = = start ( ) ) { if ( insert_position = = start ( ) ) {
dest - > set_finish ( dest - > start ( ) + finish ( ) - 1 ) ; dest - > set_finish ( dest - > start ( ) + finish ( ) - 1 ) ;
} else if ( insert_position = = kNodeValue s ) { } else if ( insert_position = = kNodeSlot s ) {
dest - > set_finish ( dest - > start ( ) ) ; dest - > set_finish ( dest - > start ( ) ) ;
} else { } else {
dest - > set_finish ( dest - > start ( ) + count ( ) / 2 ) ; dest - > set_finish ( dest - > start ( ) + count ( ) / 2 ) ;
@ -1744,7 +1777,7 @@ void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) {
// Navigate to the leftmost leaf under node, and then delete upwards.
// Navigate to the leftmost leaf under node, and then delete upwards.
while ( ! node - > leaf ( ) ) node = node - > start_child ( ) ; while ( ! node - > leaf ( ) ) node = node - > start_child ( ) ;
// Use `int` because `pos` needs to be able to hold `kNodeValue s+1`, which
// Use `int` because `pos` needs to be able to hold `kNodeSlot s+1`, which
// isn't guaranteed to be a valid `field_type`.
// isn't guaranteed to be a valid `field_type`.
int pos = node - > position ( ) ; int pos = node - > position ( ) ;
btree_node * parent = node - > parent ( ) ; btree_node * parent = node - > parent ( ) ;
@ -1832,7 +1865,7 @@ void btree_iterator<N, R, P>::decrement_slow() {
// btree methods
// btree methods
template < typename P > template < typename P >
template < typename Btree > template < typename Btree >
void btree < P > : : copy_or_move_values_in_order ( Btree * other ) { void btree < P > : : copy_or_move_values_in_order ( Btree & other ) {
static_assert ( std : : is_same < btree , Btree > : : value | | static_assert ( std : : is_same < btree , Btree > : : value | |
std : : is_same < const btree , Btree > : : value , std : : is_same < const btree , Btree > : : value ,
" Btree type must be same or const. " ) ; " Btree type must be same or const. " ) ;
@ -1840,11 +1873,11 @@ void btree<P>::copy_or_move_values_in_order(Btree *other) {
// We can avoid key comparisons because we know the order of the
// We can avoid key comparisons because we know the order of the
// values is the same order we'll store them in.
// values is the same order we'll store them in.
auto iter = other - > begin ( ) ; auto iter = other . begin ( ) ;
if ( iter = = other - > end ( ) ) return ; if ( iter = = other . end ( ) ) return ;
insert_multi ( maybe_move_from_iterator ( iter ) ) ; insert_multi ( maybe_move_from_iterator ( iter ) ) ;
+ + iter ; + + iter ;
for ( ; iter ! = other - > end ( ) ; + + iter ) { for ( ; iter ! = other . end ( ) ; + + iter ) {
// If the btree is not empty, we can just insert the new value at the end
// If the btree is not empty, we can just insert the new value at the end
// of the tree.
// of the tree.
internal_emplace ( end ( ) , maybe_move_from_iterator ( iter ) ) ; internal_emplace ( end ( ) , maybe_move_from_iterator ( iter ) ) ;
@ -1863,7 +1896,7 @@ constexpr bool btree<P>::static_assert_validation() {
// Note: We assert that kTargetValues, which is computed from
// Note: We assert that kTargetValues, which is computed from
// Params::kTargetNodeSize, must fit the node_type::field_type.
// Params::kTargetNodeSize, must fit the node_type::field_type.
static_assert ( static_assert (
kNodeValue s < ( 1 < < ( 8 * sizeof ( typename node_type : : field_type ) ) ) , kNodeSlot s < ( 1 < < ( 8 * sizeof ( typename node_type : : field_type ) ) ) ,
" target node size too large " ) ; " target node size too large " ) ;
// Verify that key_compare returns an absl::{weak,strong}_ordering or bool.
// Verify that key_compare returns an absl::{weak,strong}_ordering or bool.
@ -1883,31 +1916,29 @@ constexpr bool btree<P>::static_assert_validation() {
} }
template < typename P > template < typename P >
btree < P > : : btree ( const key_compare & comp , const allocator_type & alloc ) template < typename K >
: root_ ( comp , alloc , EmptyNode ( ) ) , rightmost_ ( EmptyNode ( ) ) , size_ ( 0 ) { } auto btree < P > : : lower_bound_equal ( const K & key ) const
- > std : : pair < iterator , bool > {
template < typename P > const SearchResult < iterator , is_key_compare_to : : value > res =
btree < P > : : btree ( const btree & other ) internal_lower_bound ( key ) ;
: btree ( other . key_comp ( ) , other . allocator ( ) ) { const iterator lower = iterator ( internal_end ( res . value ) ) ;
copy_or_move_values_in_order ( & other ) ; const bool equal = res . HasMatch ( )
? res . IsEq ( )
: lower ! = end ( ) & & ! compare_keys ( key , lower . key ( ) ) ;
return { lower , equal } ;
} }
template < typename P > template < typename P >
template < typename K > template < typename K >
auto btree < P > : : equal_range ( const K & key ) - > std : : pair < iterator , iterator > { auto btree < P > : : equal_range ( const K & key ) - > std : : pair < iterator , iterator > {
const iterator lower = lower_bound ( key ) ; const std : : pair < iterator , bool > lower_and_equal = lower_bound_equal ( key ) ;
// TODO(ezb): we should be able to avoid this comparison when there's a
const iterator lower = lower_and_equal . first ;
// three-way comparator.
if ( ! lower_and_equal . second ) {
if ( lower = = end ( ) | | compare_keys ( key , lower . key ( ) ) ) return { lower , lower } ; return { lower , lower } ;
}
const iterator next = std : : next ( lower ) ; const iterator next = std : : next ( lower ) ;
// When the comparator is heterogeneous, we can't assume that comparison with
if ( ! params_type : : template can_have_multiple_equivalent_keys < K > ( ) ) {
// non-`key_type` will be equivalent to `key_type` comparisons so there
// could be multiple equivalent keys even in a unique-container. But for
// heterogeneous comparisons from the default string adapted comparators, we
// don't need to worry about this.
if ( ! is_multi_container : : value & &
( std : : is_same < K , key_type > : : value | | is_key_compare_adapted : : value ) ) {
// The next iterator after lower must point to a key greater than `key`.
// The next iterator after lower must point to a key greater than `key`.
// Note: if this assert fails, then it may indicate that the comparator does
// Note: if this assert fails, then it may indicate that the comparator does
// not meet the equivalence requirements for Compare
// not meet the equivalence requirements for Compare
@ -1918,7 +1949,7 @@ auto btree<P>::equal_range(const K &key) -> std::pair<iterator, iterator> {
// Try once more to avoid the call to upper_bound() if there's only one
// Try once more to avoid the call to upper_bound() if there's only one
// equivalent key. This should prevent all calls to upper_bound() in cases of
// equivalent key. This should prevent all calls to upper_bound() in cases of
// unique-containers with heterogeneous comparators in which all comparison
// unique-containers with heterogeneous comparators in which all comparison
// operators are equivalent .
// operators have the same equivalence classes .
if ( next = = end ( ) | | compare_keys ( key , next . key ( ) ) ) return { lower , next } ; if ( next = = end ( ) | | compare_keys ( key , next . key ( ) ) ) return { lower , next } ;
// In this case, we need to call upper_bound() to avoid worst case O(N)
// In this case, we need to call upper_bound() to avoid worst case O(N)
@ -1934,8 +1965,8 @@ auto btree<P>::insert_unique(const K &key, Args &&... args)
mutable_root ( ) = rightmost_ = new_leaf_root_node ( 1 ) ; mutable_root ( ) = rightmost_ = new_leaf_root_node ( 1 ) ;
} }
auto res = internal_locate ( key ) ; SearchResult < iterator , is_key_compare_to : : value > res = internal_locate ( key ) ;
iterator & iter = res . value ; iterator iter = res . value ;
if ( res . HasMatch ( ) ) { if ( res . HasMatch ( ) ) {
if ( res . IsEq ( ) ) { if ( res . IsEq ( ) ) {
@ -2049,7 +2080,7 @@ auto btree<P>::operator=(const btree &other) -> btree & {
* mutable_allocator ( ) = other . allocator ( ) ; * mutable_allocator ( ) = other . allocator ( ) ;
} }
copy_or_move_values_in_order ( & other ) ; copy_or_move_values_in_order ( other ) ;
} }
return * this ; return * this ;
} }
@ -2079,7 +2110,7 @@ auto btree<P>::operator=(btree &&other) noexcept -> btree & {
// comparator while moving the values so we can't swap the key
// comparator while moving the values so we can't swap the key
// comparators.
// comparators.
* mutable_key_comp ( ) = other . key_comp ( ) ; * mutable_key_comp ( ) = other . key_comp ( ) ;
copy_or_move_values_in_order ( & other ) ; copy_or_move_values_in_order ( other ) ;
} }
} }
} }
@ -2202,31 +2233,6 @@ auto btree<P>::erase_range(iterator begin, iterator end)
return { count , begin } ; return { count , begin } ;
} }
template < typename P >
template < typename K >
auto btree < P > : : erase_unique ( const K & key ) - > size_type {
const iterator iter = internal_find ( key ) ;
if ( iter . node = = nullptr ) {
// The key doesn't exist in the tree, return nothing done.
return 0 ;
}
erase ( iter ) ;
return 1 ;
}
template < typename P >
template < typename K >
auto btree < P > : : erase_multi ( const K & key ) - > size_type {
const iterator begin = internal_lower_bound ( key ) ;
if ( begin . node = = nullptr ) {
// The key doesn't exist in the tree, return nothing done.
return 0 ;
}
// Delete all of the keys between begin and upper_bound(key).
const iterator end = internal_end ( internal_upper_bound ( key ) ) ;
return erase_range ( begin , end ) . first ;
}
template < typename P > template < typename P >
void btree < P > : : clear ( ) { void btree < P > : : clear ( ) {
if ( ! empty ( ) ) { if ( ! empty ( ) ) {
@ -2271,7 +2277,7 @@ void btree<P>::rebalance_or_split(iterator *iter) {
node_type * & node = iter - > node ; node_type * & node = iter - > node ;
int & insert_position = iter - > position ; int & insert_position = iter - > position ;
assert ( node - > count ( ) = = node - > max_count ( ) ) ; assert ( node - > count ( ) = = node - > max_count ( ) ) ;
assert ( kNodeValue s = = node - > max_count ( ) ) ; assert ( kNodeSlot s = = node - > max_count ( ) ) ;
// First try to make room on the node by rebalancing.
// First try to make room on the node by rebalancing.
node_type * parent = node - > parent ( ) ; node_type * parent = node - > parent ( ) ;
@ -2279,17 +2285,17 @@ void btree<P>::rebalance_or_split(iterator *iter) {
if ( node - > position ( ) > parent - > start ( ) ) { if ( node - > position ( ) > parent - > start ( ) ) {
// Try rebalancing with our left sibling.
// Try rebalancing with our left sibling.
node_type * left = parent - > child ( node - > position ( ) - 1 ) ; node_type * left = parent - > child ( node - > position ( ) - 1 ) ;
assert ( left - > max_count ( ) = = kNodeValue s ) ; assert ( left - > max_count ( ) = = kNodeSlot s ) ;
if ( left - > count ( ) < kNodeValue s ) { if ( left - > count ( ) < kNodeSlot s ) {
// We bias rebalancing based on the position being inserted. If we're
// We bias rebalancing based on the position being inserted. If we're
// inserting at the end of the right node then we bias rebalancing to
// inserting at the end of the right node then we bias rebalancing to
// fill up the left node.
// fill up the left node.
int to_move = ( kNodeValue s - left - > count ( ) ) / int to_move = ( kNodeSlot s - left - > count ( ) ) /
( 1 + ( insert_position < kNodeValues ) ) ; ( 1 + ( insert_position < static_cast < int > ( kNodeSlots ) ) ) ;
to_move = ( std : : max ) ( 1 , to_move ) ; to_move = ( std : : max ) ( 1 , to_move ) ;
if ( insert_position - to_move > = node - > start ( ) | | if ( insert_position - to_move > = node - > start ( ) | |
left - > count ( ) + to_move < kNodeValues ) { left - > count ( ) + to_move < static_cast < int > ( kNodeSlots ) ) {
left - > rebalance_right_to_left ( to_move , node , mutable_allocator ( ) ) ; left - > rebalance_right_to_left ( to_move , node , mutable_allocator ( ) ) ;
assert ( node - > max_count ( ) - node - > count ( ) = = to_move ) ; assert ( node - > max_count ( ) - node - > count ( ) = = to_move ) ;
@ -2308,17 +2314,17 @@ void btree<P>::rebalance_or_split(iterator *iter) {
if ( node - > position ( ) < parent - > finish ( ) ) { if ( node - > position ( ) < parent - > finish ( ) ) {
// Try rebalancing with our right sibling.
// Try rebalancing with our right sibling.
node_type * right = parent - > child ( node - > position ( ) + 1 ) ; node_type * right = parent - > child ( node - > position ( ) + 1 ) ;
assert ( right - > max_count ( ) = = kNodeValue s ) ; assert ( right - > max_count ( ) = = kNodeSlot s ) ;
if ( right - > count ( ) < kNodeValue s ) { if ( right - > count ( ) < kNodeSlot s ) {
// We bias rebalancing based on the position being inserted. If we're
// We bias rebalancing based on the position being inserted. If we're
// inserting at the beginning of the left node then we bias rebalancing
// inserting at the beginning of the left node then we bias rebalancing
// to fill up the right node.
// to fill up the right node.
int to_move = ( kNodeValues - right - > count ( ) ) / int to_move = ( static_cast < int > ( kNodeSlots ) - right - > count ( ) ) /
( 1 + ( insert_position > node - > start ( ) ) ) ; ( 1 + ( insert_position > node - > start ( ) ) ) ;
to_move = ( std : : max ) ( 1 , to_move ) ; to_move = ( std : : max ) ( 1 , to_move ) ;
if ( insert_position < = node - > finish ( ) - to_move | | if ( insert_position < = node - > finish ( ) - to_move | |
right - > count ( ) + to_move < kNodeValues ) { right - > count ( ) + to_move < static_cast < int > ( kNodeSlots ) ) {
node - > rebalance_left_to_right ( to_move , right , mutable_allocator ( ) ) ; node - > rebalance_left_to_right ( to_move , right , mutable_allocator ( ) ) ;
if ( insert_position > node - > finish ( ) ) { if ( insert_position > node - > finish ( ) ) {
@ -2334,8 +2340,8 @@ void btree<P>::rebalance_or_split(iterator *iter) {
// Rebalancing failed, make sure there is room on the parent node for a new
// Rebalancing failed, make sure there is room on the parent node for a new
// value.
// value.
assert ( parent - > max_count ( ) = = kNodeValue s ) ; assert ( parent - > max_count ( ) = = kNodeSlot s ) ;
if ( parent - > count ( ) = = kNodeValue s ) { if ( parent - > count ( ) = = kNodeSlot s ) {
iterator parent_iter ( node - > parent ( ) , node - > position ( ) ) ; iterator parent_iter ( node - > parent ( ) , node - > position ( ) ) ;
rebalance_or_split ( & parent_iter ) ; rebalance_or_split ( & parent_iter ) ;
} }
@ -2380,8 +2386,8 @@ bool btree<P>::try_merge_or_rebalance(iterator *iter) {
if ( iter - > node - > position ( ) > parent - > start ( ) ) { if ( iter - > node - > position ( ) > parent - > start ( ) ) {
// Try merging with our left sibling.
// Try merging with our left sibling.
node_type * left = parent - > child ( iter - > node - > position ( ) - 1 ) ; node_type * left = parent - > child ( iter - > node - > position ( ) - 1 ) ;
assert ( left - > max_count ( ) = = kNodeValue s ) ; assert ( left - > max_count ( ) = = kNodeSlot s ) ;
if ( 1 + left - > count ( ) + iter - > node - > count ( ) < = kNodeValue s ) { if ( 1U + left - > count ( ) + iter - > node - > count ( ) < = kNodeSlot s ) {
iter - > position + = 1 + left - > count ( ) ; iter - > position + = 1 + left - > count ( ) ;
merge_nodes ( left , iter - > node ) ; merge_nodes ( left , iter - > node ) ;
iter - > node = left ; iter - > node = left ;
@ -2391,8 +2397,8 @@ bool btree<P>::try_merge_or_rebalance(iterator *iter) {
if ( iter - > node - > position ( ) < parent - > finish ( ) ) { if ( iter - > node - > position ( ) < parent - > finish ( ) ) {
// Try merging with our right sibling.
// Try merging with our right sibling.
node_type * right = parent - > child ( iter - > node - > position ( ) + 1 ) ; node_type * right = parent - > child ( iter - > node - > position ( ) + 1 ) ;
assert ( right - > max_count ( ) = = kNodeValue s ) ; assert ( right - > max_count ( ) = = kNodeSlot s ) ;
if ( 1 + iter - > node - > count ( ) + right - > count ( ) < = kNodeValue s ) { if ( 1U + iter - > node - > count ( ) + right - > count ( ) < = kNodeSlot s ) {
merge_nodes ( iter - > node , right ) ; merge_nodes ( iter - > node , right ) ;
return true ; return true ;
} }
@ -2473,12 +2479,12 @@ inline auto btree<P>::internal_emplace(iterator iter, Args &&... args)
allocator_type * alloc = mutable_allocator ( ) ; allocator_type * alloc = mutable_allocator ( ) ;
if ( iter . node - > count ( ) = = max_count ) { if ( iter . node - > count ( ) = = max_count ) {
// Make room in the leaf for the new item.
// Make room in the leaf for the new item.
if ( max_count < kNodeValue s ) { if ( max_count < kNodeSlot s ) {
// Insertion into the root where the root is smaller than the full node
// Insertion into the root where the root is smaller than the full node
// size. Simply grow the size of the root node.
// size. Simply grow the size of the root node.
assert ( iter . node = = root ( ) ) ; assert ( iter . node = = root ( ) ) ;
iter . node = iter . node =
new_leaf_root_node ( ( std : : min < int > ) ( kNodeValue s , 2 * max_count ) ) ; new_leaf_root_node ( ( std : : min < int > ) ( kNodeSlot s , 2 * max_count ) ) ;
// Transfer the values from the old root to the new root.
// Transfer the values from the old root to the new root.
node_type * old_root = root ( ) ; node_type * old_root = root ( ) ;
node_type * new_root = iter . node ; node_type * new_root = iter . node ;
@ -2501,61 +2507,51 @@ template <typename P>
template < typename K > template < typename K >
inline auto btree < P > : : internal_locate ( const K & key ) const inline auto btree < P > : : internal_locate ( const K & key ) const
- > SearchResult < iterator , is_key_compare_to : : value > { - > SearchResult < iterator , is_key_compare_to : : value > {
return internal_locate_impl ( key , is_key_compare_to ( ) ) ;
}
template < typename P >
template < typename K >
inline auto btree < P > : : internal_locate_impl (
const K & key , std : : false_type /* IsCompareTo */ ) const
- > SearchResult < iterator , false > {
iterator iter ( const_cast < node_type * > ( root ( ) ) ) ;
for ( ; ; ) {
iter . position = iter . node - > lower_bound ( key , key_comp ( ) ) . value ;
// NOTE: we don't need to walk all the way down the tree if the keys are
// equal, but determining equality would require doing an extra comparison
// on each node on the way down, and we will need to go all the way to the
// leaf node in the expected case.
if ( iter . node - > leaf ( ) ) {
break ;
}
iter . node = iter . node - > child ( iter . position ) ;
}
return { iter } ;
}
template < typename P >
template < typename K >
inline auto btree < P > : : internal_locate_impl (
const K & key , std : : true_type /* IsCompareTo */ ) const
- > SearchResult < iterator , true > {
iterator iter ( const_cast < node_type * > ( root ( ) ) ) ; iterator iter ( const_cast < node_type * > ( root ( ) ) ) ;
for ( ; ; ) { for ( ; ; ) {
SearchResult < int , true > res = iter . node - > lower_bound ( key , key_comp ( ) ) ; SearchResult < int , is_key_compare_to : : value > res =
iter . node - > lower_bound ( key , key_comp ( ) ) ;
iter . position = res . value ; iter . position = res . value ;
if ( res . match = = MatchKind : : kEq ) { if ( res . IsEq ( ) ) {
return { iter , MatchKind : : kEq } ; return { iter , MatchKind : : kEq } ;
} }
// Note: in the non-key-compare-to case, we don't need to walk all the way
// down the tree if the keys are equal, but determining equality would
// require doing an extra comparison on each node on the way down, and we
// will need to go all the way to the leaf node in the expected case.
if ( iter . node - > leaf ( ) ) { if ( iter . node - > leaf ( ) ) {
break ; break ;
} }
iter . node = iter . node - > child ( iter . position ) ; iter . node = iter . node - > child ( iter . position ) ;
} }
// Note: in the non-key-compare-to case, the key may actually be equivalent
// here (and the MatchKind::kNe is ignored).
return { iter , MatchKind : : kNe } ; return { iter , MatchKind : : kNe } ;
} }
template < typename P > template < typename P >
template < typename K > template < typename K >
auto btree < P > : : internal_lower_bound ( const K & key ) const - > iterator { auto btree < P > : : internal_lower_bound ( const K & key ) const
- > SearchResult < iterator , is_key_compare_to : : value > {
if ( ! params_type : : template can_have_multiple_equivalent_keys < K > ( ) ) {
SearchResult < iterator , is_key_compare_to : : value > ret = internal_locate ( key ) ;
ret . value = internal_last ( ret . value ) ;
return ret ;
}
iterator iter ( const_cast < node_type * > ( root ( ) ) ) ; iterator iter ( const_cast < node_type * > ( root ( ) ) ) ;
SearchResult < int , is_key_compare_to : : value > res ;
bool seen_eq = false ;
for ( ; ; ) { for ( ; ; ) {
iter . position = iter . node - > lower_bound ( key , key_comp ( ) ) . value ; res = iter . node - > lower_bound ( key , key_comp ( ) ) ;
iter . position = res . value ;
if ( iter . node - > leaf ( ) ) { if ( iter . node - > leaf ( ) ) {
break ; break ;
} }
seen_eq = seen_eq | | res . IsEq ( ) ;
iter . node = iter . node - > child ( iter . position ) ; iter . node = iter . node - > child ( iter . position ) ;
} }
return internal_last ( iter ) ; if ( res . IsEq ( ) ) return { iter , MatchKind : : kEq } ;
return { internal_last ( iter ) , seen_eq ? MatchKind : : kEq : MatchKind : : kNe } ;
} }
template < typename P > template < typename P >
@ -2575,7 +2571,7 @@ auto btree<P>::internal_upper_bound(const K &key) const -> iterator {
template < typename P > template < typename P >
template < typename K > template < typename K >
auto btree < P > : : internal_find ( const K & key ) const - > iterator { auto btree < P > : : internal_find ( const K & key ) const - > iterator {
auto res = internal_locate ( key ) ; SearchResult < iterator , is_key_compare_to : : value > res = internal_locate ( key ) ;
if ( res . HasMatch ( ) ) { if ( res . HasMatch ( ) ) {
if ( res . IsEq ( ) ) { if ( res . IsEq ( ) ) {
return res . value ; return res . value ;
